Apparatus for phototherapy of the eye

ABSTRACT

A device and method for applying light to the cornea of the eye as, for example, to promote crosslinking of collagen in the cornea for vision correction. The device may include a structure having form and size similar to a conventional contact lens. The structure may include an optically dispersive element such as a mass of an optically dispersive material that may be contained in a cavity of a reflective element. Light applied to the dispersive mass as, for example, by an optical fiber connected to the structure is dispersed in the structure and passes into the cornea. The patient may blink or close the eye during the procedure, which increases patient comfort and aids in maintaining hydration of the cornea.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/314,518, filed Jun. 25, 2014, which application claims thebenefit of the filing date of U.S. Provisional Patent Application No.61/839,016 filed Jun. 25, 2013, the disclosures of which are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present application relates generally to devices for applying lightsuch as ultraviolet (“UV”) light to the cornea of the eye; to methods ofmanufacturing such devices; and to methods of applying phototherapy tothe eye.

In humans and other mammals, the eye includes a clear, dome-shapedelement referred to as the cornea disposed at the front of the eye.Light passes into the eye through the cornea and, after passing throughother structures such as the iris and the lens of the eye, ultimatelyimpinging on the retina. The light impinging on the retina is convertedto neural impulses that are processed to form the visual images. Thecornea and the lens refract the light passing through them. In a healthyeye, the refraction imparted by the cornea and the lens focuses thelight on the retina.

Most of the light refraction required for the primary focusing on theretina is done by the cornea, with the lens making the accommodativechanges to move focus from close to distant objects. Mismatches betweenthe corneal curvature and the axial length of the eye, imperfections inthe shape of the cornea, malpositions of the lens, and error in thevitreous of the eye can all lead to vision errors. For example, an eyethat has a cornea that focuses the light in front of the retina (an eyewith too much curvature relative to the axial length of the eye) suffersfrom myopia (also referred to as near-sightedness). Conversely, a corneathat is not curved enough for the axial length results in hyperopia(also referred to as far-sightedness), where the focal point is behindthe retina. Astigmatism is an uneven curvature of the cornea withrespect to the shape of the retina. All three conditions result in anout of focus image formed on the retina. Beyond these errors incurvature that affect healthy eyes, pathological conditions such askeratoconus and corneal ectasia result in unstable corneas and impairedvision.

Eyeglasses and contact lenses can correct conditions such as myopia,hyperopia and astigmatism by adding an artificial refractive element tothe system. However, these devices impose some inconvenience on thepatient. Accordingly, refractive surgical therapies such as radialkeratotomy and laser ablation of the cornea have been developed. Theseprocedures correct vision by reshaping the cornea so as to alter itsrefractive properties. However, these procedures have certain drawbacksand can have undesirable side effects.

In a technique known as orthokeratolgy, the cornea is mechanicallyreshaped by applying a rigid contact lens having a shape different fromthe existing shape of the cornea. The lenses are worn overnight.However, changes in shape induced by orthokeratology are temporary. Theytypically last only 24-48 hours, after which the cornea reverts to itsoriginal shape.

In yet another technique, the cornea can be reshaped by crosslinkingfibers of collagen which form part of the cornea. The crosslinking canbe performed by applying UV light to the cornea in conjunction with achemical agent such as riboflavin. Typically, the UV light is applied bydirecting UV light from one or more light emitting diodes (“LEDs”) minto the patient's eye, substantially perpendicular to the surface ofthe cornea. The crosslinking strengthens the cornea and can also causereshaping of the cornea Procedures of this type require that the patientkeep the treated eye open for a prolonged period without blinking. Thiscreates discomfort for the patient and also requires close monitoring bytrained personnel to assure that the cornea remains hydrated.

It has also been proposed to apply crosslinking in conjunction withorthokeratology. In this approach, the crosslinking is performed aftermechanical reshaping or while the cornea is held mechanically in thedesired shape. The crosslinking acts to set the cornea and preventreversion of the cornea to its original shape. For example, Mrochen etal., U.S. Published Patent Application No. 2008/0208177, proposes athick, rigid mold equipped with an array of light emitting diodes or“LED's.” While the mold is applied to the cornea, the LED's emit UVlight in the direction toward the surface of the cornea. The mold mayinclude a diffuser plate interposed between the LED's and the cornea tomake the light impinging on the cornea more uniform. In another variant,the array of LED's and the diffuser plate is replaced by a branchingarray of “optical light guides” extending to numerous points on thesurface of the cornea. Structures of this type still require that thepatient keep his or her eye open during the treatment, without blinking.

Chuck et al., U.S. Published Patent Application No. 2013/0211389,discloses a treatment device which incorporates radiation-emittingelements such as LEDs, along with the circuitry required to drive theseelements, into a device having size and shape resembling a conventionalcontact lens. Using this device, the patient can blink or keep his orher eye shut while receiving crosslinking therapy. This provides a morecomfortable patient experience, greatly reduces the risk of cornealdehydration during the therapy, and also reduces the need for constantmonitoring of hydration by medical personnel. However, LEDs andcircuitry incorporated into the device evolve heat during operation.Therefore, the power which can be applied by the device must berestricted.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention provides a device for applying lightto the eye of a human or other mammalian subject. A device according tothis aspect of the present invention desirably includes a contact lensstructure having a first inner surface generally corresponding to theshape of the cornea. Optionally, the device may have a second interiorsurface corresponding to the shape of the sclera. The contact lensstructure desirably includes an optically dispersive element. Theoptically dispersive element desirably is constructed and arranged sothat light passing into the optically dispersive element in a directiongenerally parallel to the inner surface will be dispersed and at leastsome of the dispersed light will pass through the inner surface of thecontact lens structure into the cornea.

The optically dispersive element may include an optically dispersivefiber. The optically dispersive fiber may be arranged in one or moreloops encircling a central axis of the contact lens structure.Alternatively or additionally, the optically dispersive element mayinclude an optically dispersive mass, and the mass may have an innersurface having a shape generally conforming to the shape of the cornea.In certain embodiments, the structure includes both an opticallydispersive fiber and an optically dispersive mass. The opticallydispersive fiber may be in optical communication with the opticallydispersive mass, so that light dispersed by the fiber will pass into themass, and will be further dispersed by the mass and pass into thecornea. Desirably, the structure includes a reflector that defines acavity encompassing the dispersive mass. In one arrangement, atransmission optical fiber has a distal end disposed within the cavity,and the light is dispersed by the dispersive mass and passes out throughan aperture in the reflector.

The entire contact lens structure may be formed as a shell generallyconforming to the shape of the eye. The thickness of the shell may besimilar to that of a conventional contact lens as, for example, lessthan about 1 mm thick.

A further aspect of the present invention provides methods of applyingphototherapy to the eye of human or other mammalian subject. A methodaccording to this aspect of the invention desirably includes directinglight into a structure generally in the form of a shell similar in formand size to a contact lens, desirably less than 3 mm thick, overlyingthe eye and dispersing the light within the structure so that thedispersed light passes out of the structure and into the cornea of theeye. For example, the step of directing light into the contact lensstructure may include directing light into the structure through atransmission fiber connected to the contact lens structure. The lightmay be UV light, and the method may further include the step of applyinga photoactivated cross-linking agent to the eye so that thecross-linking agent is present when the light passes into the eye. Themethod desirably further includes the step of allowing the subject toclose his or her eyelids over the contact lens structure while the lightis being applied.

Methods and apparatus according to certain embodiments of the inventioncan provide effective phototherapy, such as effective cross-linking,without requiring the patient to keep his or her eye open during theprocedure, or to lie down facing a light source. This greatly enhancesthe comfort and practicality of the procedure. Moreover, the methods andapparatus according to these embodiments of the invention do not requirethe complex and expensive apparatus used to direct light into the eyeheretofore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic perspective view depicting a component of adevice in accordance with one embodiment of the invention.

FIG. 2 is a further diagrammatic perspective view depicting thecomponent of FIG. 1 in conjunction with another component.

FIG. 3 is a diagrammatic partially sectional perspective view depictingthe components of FIGS. 1 and 2 in conjunction with still furthercomponents of the device.

FIG. 4 is a fragmentary, diagrammatic sectional view depicting thecomponents of FIGS. 1-3 in conjunction with still further components ofthe device.

FIG. 5 is a diagrammatic sectional view depicting the deviceincorporating the components of FIGS. 1-4.

FIG. 6 is a diagrammatic plan view depicting the device of FIG. 5.

FIG. 7 is a diagrammatic sectional view depicting the device of FIGS.1-5 in conjunction with a human eye.

FIG. 8 is a diagrammatic plan view depicting a device in accordance witha further embodiment of the invention.

FIG. 9 is a view similar to FIG. 7, but depicting yet another embodimentof the invention.

FIG. 10 is a diagrammatic plan view depicting a device according to yetanother embodiment of the invention.

FIG. 11 is a diagrammatic plan view of a device in accordance with yetanother embodiment of the invention.

FIGS. 12 and 13 are diagrammatic, partially schematic block-diagramdepictions of devices in accordance with still further embodiments ofthe invention.

FIG. 14 is a schematic diagram of a component used in the device of FIG.13.

FIG. 15 is a schematic depiction of a device according to a furtherembodiment of the invention.

FIG. 16 is a circuit diagram of an element used in the device of FIG.15.

FIGS. 17 and 18 are diagrammatic plan views of elements used in furtherembodiments of the invention.

FIG. 19 is a diagrammatic, partially sectional view of a deviceaccording to a further embodiment of the invention.

FIGS. 20 and 21 are fragmentary sectional views of the device shown inFIG. 19.

FIG. 22 is a view similar to FIG. 20, but depicting a device accordingto yet another embodiment of the invention.

FIG. 23 is a fragmentary, diagrammatic sectional view depicting aportion of a device according to a further embodiment of the invention.

FIG. 24 is a diagrammatic sectional view depicting a device according toa still further embodiment of the invention.

FIG. 25 is a diagrammatic sectional view depicting a device according toyet another embodiment of the invention.

DETAILED DESCRIPTION

A device according to one embodiment of the invention incorporates afirst optically dispersive element in the form of a radially dispersiveoptical fiber 20 (FIG. 1). As used in this disclosure, the term“optically dispersive element” refers to an element that is adapted toscatter light propagating in a direction of propagation so that anappreciable portion of such light is redirected in directions transverseto the direction of propagation. The term “dispersive” is used hereininterchangeably with the term “scattering”, and has the same meaning asdiscussed in the foregoing sentence. The term “radially dispersiveoptical fiber” refers to a fiber, such as fiber 20, which is adapted toallow propagation of light along the length of the fiber while alsoscattering an appreciable portion of the light propagating along thefiber in directions transverse to the length of the fiber.

The degree of dispersion in an optical fiber can be stated in terms ofits “extinction length.” With respect to a fiber, the extinction lengthas referred to in this disclosure is the length along the direction ofpropagation in which light transmitted from a starting point along thelength of the fiber loses 90% its power. Stated another way, theextinction length of a fiber is the length of fiber over which 90% ofthe incoming light is dispersed and thus emitted out of the fiber indirections transverse to the length of the fiber. Radially dispersiveoptical fibers having essentially any desired extinction length areavailable from sources including Corning Glass Works of Corning, N.Y.,USA. As further discussed below, the desired extinction length dependsin part on the length of radially dispersive fiber incorporated into thedevice. However, typical designs incorporate optical fibers havingextinction lengths on the order of 0.5-4 meters.

Fiber 20 is arranged in one or more loops extending around a centralaxis 22. In the particular embodiment depicted, fiber 20 is arranged ina spiral of approximately two full turns constituting the loops. Theinner turn 21 a has an average diameter slightly larger than thediameter of an area of the cornea to be treated. Thus, the total lengthof fiber incorporated in the turns is about 25 mm. Most typically, theratio of the length of radially dispersive optical fiber incorporated inthe one or more loops to the extinction length of the optical fiber is0.05:1 to 0.3:1, most typically about 0.2:1 to 0.3:1. As furtherexplained below, the ratio is selected in conjunction with other designfeatures to enhance the uniformity of light distribution achieved by thesystem.

The end 23 of the inner turn 21 a is referred to herein as thetermination end of the dispersive fiber. Termination end 23 is coveredby a coating 25 adapted to absorb UV light. The outer end of the outerturn 21 b constitutes the input end of the fiber in the loops. Theradially dispersive optical fiber includes a short stub 24 extending outfrom the outer end of the outer turn 21 b. Stub 24, and hence fiber 20,is connected to the distal end of a conventional, substantiallynon-dispersive transmission optical fiber 26 by a splice 28. Forexample, splice 28 may be a fusion splice made by fusing the ends offibers 20 and 26 to one another or a mechanical coupling holdingpolished ends of the fibers in precise alignment with one another. Stub24, splice 28 and transmission fiber 26 are referred to collectively asthe input fiber system. The input fiber system may be covered with aconventional jacket or other protective element (not shown), so as toprotect it from physical damage. However, the distal portion of theinput fiber system adjacent the loops, including any jacket coveringthis portion of the fiber system, desirably is of relatively smalldiameter as, for example, 0.6 mm or less and more preferably 0.25 mm orless. As explained below, this helps to minimize irritation to thepatient's eyelids in use of the device.

The proximal end of transmission fiber 26 is releasably connected to aUV light source 30, as by a conventional connector (not shown). Source30 may be a conventional device such as a UV laser arranged to emitlight at the desired wavelength for the therapy to be performed. Wherethe device is to be used in cross-linking of the cornea using riboflavinas a cross-linking agent, the light may be near UV light of 360 nm to380 nm wavelength or blue light of about 425 nm to 475 nm wavelength.

The device further includes a fiber carrier 34 (FIGS. 2, 3) formed froma transparent material, preferably a polymer such as an acrylic. Thefiber carrier is shown as opaque in FIG. 2 for illustrative purposesonly. The transparent material of the fiber carrier will transmit UVlight substantially without dispersion.

Fiber carrier 34 is generally in the form of a shallow dome with aconcave interior surface 36, a convex exterior surface 38, and a hole 40extending between the interior and exterior surfaces at the center ofthe dome. The fiber carrier 34 also defines a generally cylindrical edgesurface 42 extending between the interior and exterior surfaces. As bestseen in FIG. 4, the juncture between edge surface 42 and exteriorsurface 38 is provided with a radius 48 so that the edge surface 42 andexterior surface 38 merge gradually into one another.

The exterior surface 38 of the fiber carrier has a spiral groovedefining an inner turn 46 a and an outer turn 46 b corresponding to theturns 21 a and 21 b of radially dispersive optical fiber 20. The outerturn 46 b of the spiral groove terminates at an opening 48 extendingthrough edge surface 42 of the fiber carrier. Turns 21 a and 21 b offiber 20 are disposed in the turns 46 a and 46 b of the spiral groove,respectively. Thus, the axis 22 of fiber turns 21 a and 21 b also formsthe central axis of the fiber carrier. The stub 24 of fiber 20 extendsout of the fiber carrier through opening 48. A transparent filler 49(FIG. 4) is disposed within the turns 46 a and 46 b of the groove. Thefiller defines surfaces that are flush with the exterior surface 38 ofthe fiber carrier. The features of the lens carrier, such as the edgesurface 42 and the interior surface of hole 40, are substantially in theform of surfaces of revolution about the central axis 22.

The device further includes a mass 50 of an optically dispersivematerial disposed within the hole 40 in the fiber carrier 34. Forexample, mass 50 may be formed from a transparent silicone polymerhaving microscopic particles of an opaque, reflective material such astitanium, titanium dioxide, or zinc dispersed throughout the polymer.The dispersive properties of a material of this nature can be controlledby varying parameters such as the particle material, the ratio ofparticles to polymer, the size of the particles, and the shape of theparticles.

Mass 50 is in the form of a dome-like shell having a concave interiorsurface 52 and a convex exterior surface 54. These surfaces generallyconform to the dome-like configuration of the fiber carrier 34, so thatthe fiber carrier and shell 50 form a continuous dome-like structurehaving substantially smooth interior and exterior surfaces. Shell 50also has a generally cylindrical edge surface 56 extending betweensurfaces 52 and 54 and abutting the inner surface of the fiber carrier34, which defines hole 40. Shell 50 can be formed by casting it in placein the hole 40 of the fiber carrier while holding the fiber carrier in amold defining the desired dome shape.

Shell 50 constitutes a second optically dispersive element. Here again,the degree of dispersion in such an element can be characterized by theextinction length of the element. This embodiment is intended to produceuniform irradiation intensity across the area of the cornea to betreated. In this case, the extinction length of the mass or shell 50typically is greater than the diameter of the cylindrical edge surface50.

A reflective element in the form of a film 58, best seen in FIG. 4,covers the interior and exterior surfaces 36 and 38 of the fiber carrierand also covers the edge surface 42 of the fiber carrier and thetransition 44 between the edge surface and the exterior surface. Forexample, film 58 may be formed from aluminum or other metals. Film 58also covers the entire exterior surface 54 of dispersive shell 50. Film58 may extend beyond the edge surface 56 of the shell so that the filmmay cover a portion of the interior surface 52 of the dispersive shellremote from the central axis 22 of the device. However, a portion of theinterior surface 52 adjacent the axis is left uncovered by the metallicfilm 58, so as to define an aperture 60 surrounding axis 22. As bestappreciated with reference to FIG. 4, the reflective element 58 forms acavity, and the dispersive mass 50 is disposed within this cavity. Thereflective element 58 includes a reflective circumferential surfaceoverlying the edge surface 42 of the wafer carrier and extending aroundaxis 22. This reflective circumferential surface is in opticalcommunication with the edge surface 56 of mass 50, through the clearfiber carrier 34. The reflective element 58 also includes a surfacefacing in an inward direction, toward the bottom of the drawing,overlying the outer surface 54 of mass 50, as well as an outwardlyfacing ledge surface overlying the inner surface 36 of the fibercarrier.

This embodiment is intended to correct myopia by flattening the cornea.For this purpose, the aperture is generally circular and has a radiusapproximately equal to the radius of a portion of the cornea to betreated. The aperture size appropriate for the particular patient isselected by the ophthalmologic professional. That is, aperture 60 issized to cover only a portion of the cornea adjacent the center of thecornea. As explained below, this will provide crosslinking near thecenter of the cornea, so as to treat myopia.

Film 58 may be on the order of a few microns to a few tens of micronsthick. Merely by way of example, film 58 may be formed by conventionalmethods of depositing metals onto polymers as, for example, electrolessplating followed by electroplating, vapor deposition, sputtering, or thelike. Alternatively, the reflective metallic element may be formed byother metalworking methods such as stamping, die casting or machining.

The assemblage of the fiber carrier, radially dispersive fiber,dispersive shell, and reflective element is embedded in a housing 62.Housing 62 has a dome-like central portion defining a first interiorsurface 64 with a shape adapted to conform to the shape of the cornea.The housing also includes a skirt portion defining a second interiorsurface 66 surrounding the first interior surface. The second interiorsurface has a shape adapted to conform to the shape of the sclera oropaque portion of the eye surrounding the cornea. The assemblage of thefiber carrier 34 and shell 50 is mounted centrally in housing 62 so thatthe central axis 22 defined by the fiber and fiber carrier is coincidentwith the central axis of dome-like portion 64 of the housing. Housing 62also has an exterior surface 68 extending generally parallel to theinterior surface portions 64 and 66 and covering the exterior surfacesof fiber carrier 34 and shell 50. As best seen in FIG. 4, housing 68includes a thin interior film 70 covering the interior surfaces of thefiber carrier 34 and shell 50 and overlying metallic film 58 on theinterior surface of the fiber carrier. Housing 62, apart from interiorfilm 70, may be formed from essentially any material, but typically isformed from a relatively soft polymer such as silicone. Interior film 70desirably is formed from a material having good compatibility with thetissues of the eye as, for example, a hydrophilic polymer. The materialof film 70 should also be capable of transmitting the light to beapplied.

As best appreciated with reference to FIG. 5, the housing 62, fibercarrier 34, and shell 50 cooperatively form a contact lens structuresubstantially in the form and shape of a conventional scleral fitcontact lens. Thus, the entire structure forms a relatively thin shellhaving interior and exterior surfaces generally conforming to the shapeof the cornea and sclera. The thickness T of the entire contact lensstructure desirably is no more than 3 mm, preferably no more than 2 mm,more preferably less than 1 mm, and most preferably less than 800 μm.

As best seen in FIG. 6, the fiber system (stub 24, transmission fiber 26and splice 28) extends out the housing 28 in a direction transverse tothe central axis 22. The fiber system exits the housing at an angle Arelative to a line tangent to a circle concentric with central axis 22and passing though the exit point. Angle A may have any value, including0°, such that the fiber system exits parallel to the tangent line, and90°, such that the fiber system exits perpendicular to the tangent line.Typically, an angle between 0° and 90° is chosen to mitigate bothmanufacturing challenges and contact with the patient's eyelid duringthe use of the device.

In a method according to a further embodiment of the invention, a deviceas discussed above with reference to FIGS. 1-6 is placed over the frontsurface of the eye of a human or other mammalian subject as depicted inFIG. 7. The interior surfaces of the housing 62, fiber carrier 34, anddispersive shell 50 overlie the exterior surfaces of the sclera 72 andcornea 74 of the subject's eye. Typically, those portions of the deviceoverlying the cornea are spaced slightly from the cornea so as toprovide a small space between the outer surface of the cornea and theinner surface of the device. The central axis 22 of the device issubstantially aligned with the central axis of the subject's eye. Thecentral axis of the subject's eye, as referred to in this disclosure, isthe axis extending through the center of the cornea and the center ofthe lens 76 of the eye, as well as the center of the pupil 78 of theeye. In this orientation, the fiber turns 21 a, 21 b extend generally inplanes transverse to the central axis of the eye, as indicatedschematically by plane 80 in FIG. 6. Thus, the turns of the radiallydispersive optical fiber extend generally parallel to the surface of theeye. Likewise, the interior and exterior surfaces of dispersive shell 50extend generally parallel to the surface of the eye, and specificallythe surface of the cornea. Also, the turns of the fiber surround thecentral axis of the eye, which, again, is substantially coincident withthe central axis 22 of the device.

Before or during the application of the device to the eye, the eye istreated with a photo-reactive crosslinking agent 75 such as riboflavinand the crosslinking agent is allowed to permeate into the cornea 74. Asseen in FIG. 7, the device may be used as a reservoir to trap the agentin contact with the cornea during permeation. After a the agent haspermeated into the cornea, and before light is applied as discussedbelow, the agent desirably is removed from the space between the deviceand the cornea as, for example, by flushing this space with a liquidsuch as saline solution or the patient's natural tears. Alternatively,the agent may be confined in contact with the cornea by another devicesuch as another contact lens shaped shell, which is removed and replacedby the device. Optionally the epithelial layer forming the outermostsurface of the cornea may be removed or disrupted using conventionaltechniques so as to enhance permeation of the crosslinking agent intothe collagen of the cornea.

While the crosslinking agent is present in the cornea, the light source30 (FIG. 1) is actuated so as to direct light at a wavelength suitablefor activating the crosslinking agent through the transmission fiber 26and into dispersive fiber 20. Where the agent is riboflavin, the lightmay be near UV light of 360 nm to 380 nm wavelength or blue light ofabout 425 nm to 475 nm wavelength. The light enters through stub 24 ofthe dispersive fiber 20 and passes lengthwise along the fiber throughturns 21 a and 21 b. Thus, the light passing along the dispersive fiberin turns 21 a and 21 b is directed generally parallel to the surface ofthe eye. As the light passes along the turns of the fiber, a portion ofthe light is dispersed from the fiber, and the dispersed portionpropagates in directions transverse to the length of the fiber, asindicated by arrows 82 (FIG. 4). The light dispersed from the fiberspasses through the transparent material of fiber carrier 34 into thedispersive shell 50 through the edge surface 56 of the shell. Some ofthe light dispersed by the fibers passes directly into the shell asindicated by arrow 82 a in FIG. 4. Other light dispersed from by fiberpasses into shell 50 by indirect paths, including one or morereflections from reflective film 58, as indicated by arrows 82 b and 82c in FIG. 4. A substantial portion of the light directed into shell 50through peripheral surface 56 is propagating in directions generallyparallel to the interior surface 52 of the shell and thus generallyparallel to the surface of the cornea. As used in this disclosure, apropagation direction can be considered “generally parallel” to asurface if the propagation direction forms an angle of less than about45° and preferably less than 30° to the surface.

The light propagating through dispersive shell 50 is dispersed. Some ofthe light dispersed in the shell is directed in the inward direction,towards the inner surface 52 of the shell. This light passes through theaperture 60 (FIG. 4) and into the cornea 74. Of course, dispersion inshell 50 is omnidirectional, and some of the light dispersed by thematerial of the shell will travel in directions other than the inwarddirection. Light initially dispersed in the outward direction will bereflected back toward the cornea by the metallic film 58 overlying theouter surface. Light dispersed in directions parallel to the inner andouter surfaces of the shell may pass out of the dispersive shell 50,through the edge surface 56, and into the transparent material of thefiber carrier 34, but will be reflected back into the shell by film 58.Likewise, some of the light passing from the fibers into the dispersiveshell 50 will travel entirely across the dispersive shell and out intothe fiber carrier 34 at another location. This light also will bereflected back into the shell by film 58. Film 58 is not perfect, andsome light will be lost during internal reflection. However, asubstantial portion of the light dispersed by the fiber will ultimatelypass out of the dispersive mass 50 through aperture 60 and into thecornea. The pattern of light travel discussed above is substantiallysymmetrical around the entire circumference of the device.

As the light passes from the inlet fiber 26 through the radiallydispersive fiber 20, it diminishes in intensity. Accordingly, slightlyless light will be dispersed from the fiber near the terminal end 23 ofthe fiber than near the input end and stub 24. However, this differencetypically is minor. As pointed out above, the extinction length of thefiber is substantially greater than the length of fiber constitutingturns 21 a and 21 b. Moreover, this difference is taken up over two fullturns, i.e., 720° of travel in the circumferential direction aroundcentral axis 22. Thus, the circumferential non-uniformity is minimal.Moreover, the effects of the multiple reflections and multiple passes oflight through the dispersive shell 50, as discussed above, compensatefor any non-uniformity in the light dispersed from the fiber. Desirably,the light passing out from aperture 60 (FIG. 4) is of uniform intensityover the entire surface area of the aperture to within about 20% orless.

The system is actuated to provide a dose of light to the corneasufficient to perform the desired crosslinking. Merely by way ofexample, a dose of about 5.4 Joules/cm² may be delivered over a periodof about 30 minutes in a typical procedure. While the device is presentin the subject's eye, the subject may close his or her eye and blinkfreely to provide hydration to the eye. The thin contact lens-likestructure of the device allows the patient to do this withoutdiscomfort. When the patient closes the eye or blinks, the eyelids closeover and around the distal portion of the fiber system. The smalldiameter of the fiber system limits any discomfort caused by the fiber.The patient's eyelids desirably are not held open by an ophthalmologyspeculum or other device. Moreover, the patient's head does not have tobe retained in a fixed position during the procedure.

The device and procedure discussed above may be varied in many ways. Inone such variant, the coating 25 on the termination end 23 of the fiberis reflective rather than light-absorbing. In this variant, light whichreaches the termination end of the dispersive fiber is reflected backtoward the input end. The reflected light is also dispersed by thefiber, so that the intensity of the reflected light diminishes as ittravels toward the input end of the fiber. By contrast, the lightoriginally supplied through to the fiber at its input end diminishes inintensity as it travels toward the termination end. These effectscounteract one another to reduce non-uniformity in the amount of lightdispersed along the length of the fiber.

The radially dispersive optical fiber used in the embodiments discussedabove may incorporate any number of loops as, for example, a single loopor three or more loops. The turns 21 a and 21 b of the spiral dispersivefiber 20 discussed above form loops extending around the central axis ofthe device. In other structures, where multiple loops are desired, thesecan be provided as separate radially dispersive optical fibers.

The fiber carrier 34 and filler 49 discussed above with reference toFIGS. 3 and 4 may be replaced by a unitary mass of a clear material suchas an epoxy or an acrylic which secures the dispersive fiber in one ormore loops. The fiber may be embedded in the clear material as, forexample, by casting the material around the fiber. In yet anothervariant, the clear material may serve as an adhesive so as to secure thefiber to another structural element of the device as, for example, thereflective element 58. In yet another variant, the fiber may be embeddedin the dispersive mass. For example, in the embodiment discussed above,the dispersive mass 50 may include a peripheral portion which occupiesthe space remote from the central axis occupied by the fiber carrier 34in FIGS. 3-5. The dispersive fiber loops may be embedded in thisperipheral portion of the dispersive mass, so that a central portion ofthe dispersive mass is disposed inside the loops.

The skirt portion of the housing 62 defining the second interior surface66 depicted in FIG. 5 may be omitted. In this variant, the device hasthe form and shape of a conventional corneal contact lens.

The embodiment discussed above with reference to FIGS. 1-7 is intendedto provide substantially uniform light intensity over the entireaperture. However, an intensity gradient in radial directions, towardsand away from central axis 22, may be provided by adjusting theproperties of the dispersive mass. For example, the dispersive mass mayhave properties which vary with location within the mass as, forexample, an extinction length which varies in the radial direction. Inanother example, the dispersive mass may be of uniform properties, butthese properties may be selected to provide the desired gradient. Forexample, a mass having a short extinction length can produce a radialgradient.

In the embodiment discussed above, light application and, hence,crosslinking occurs only over a central portion of the cornea. Thistends to flatten the central portion and thus correct some or all of apatient's myopic error. A device according to a further embodiment ofthe invention (FIG. 8) has a dispersive shell 150 and other elements(not shown) similar to those discussed above with reference to FIGS.1-6. However, the reflective film is patterned so that the aperture 160is in the form of an annulus surrounding the central axis 122 of thedevice. Thus, the reflective film on the interior surface of the deviceincludes a main portion 158 a defining the outside of the annulus and adisc-like central portion 158 b overlying a region immediatelysurrounding axis 122. This device may be used to treat hyperopia. Thus,the UV light will be applied to a ring-shaped zone of the cornea, remotefrom the central axis of the eye, the parameters of which are selectedto optimize the corneal shape change, thus tending to increase thecurvature of the cornea.

A device according to yet another embodiment (FIG. 9) incorporates adispersive shell 250 and associated fiber (not shown) similar to thecorresponding elements of the device discussed above with reference toFIGS. 1-7. In this embodiment, however, the reflective film 258 ispatterned so as to provide an aperture that is non-uniform in thecircumferential direction around axis 222. In the particular embodimentshown, the aperture 260 includes two generally triangular, diametricallyopposed portions, so that the aperture as a whole defines a “butterfly”shape. A structure according to this embodiment can be used to treatastigmatism. In this embodiment, the device is positioned on the eye sothat the butterfly shape corresponds to a particular region of the eyewhere UV light application and crosslinking are desired. To aid in thisprocess, the exterior surface of the device may have a mark indicatingthe orientation of the butterfly-shaped aperture. Also, the device mayhave a weight or other element to aid in maintaining the desiredorientation during the treatment. Alignment also may be controlled bywhere the on the circumference of the device the fiber exits and theexit angle A discussed above with reference to FIG. 6.

A device according to a further embodiment of the invention (FIG. 10)includes only one optically dispersive element in the form of a radiallydispersive optical fiber 320. The dispersive fiber 320 may be arrangedin the form of a spiral extending around the central axis 322 of thehousing. As in the embodiments discussed above, housing 362 may have theform and size of a scleral contact lens or a corneal contact lens. Thespiral fiber may be disposed along a generally dome-like or disc-likesurface of the housing extending transverse to the central axis 322 ofthe housing 362 of the device and facing toward the inner side of thehousing. A reflective element (not shown) may be interposed between thefiber and the housing. The fiber may be secured to the housing surfaceor to the surface of the reflective element by a clear adhesive. In thisarrangement, light dispersed from the fiber may pass directly into thecornea without passing through another optically dispersive element. Inanother arrangement, one or more optically dispersive layers (not shown)may be provided. For example, the adhesive that secures the fiber to thehousing or reflective element may be optically dispersive. Thedispersive adhesive may be disposed between turns of the spiral, andalso may form a layer covering the fiber spiral on the side facingtoward the eye. Alternatively or additionally, one or more otherdispersive layers may be provided between the fiber and the eye. Asdepicted in FIG. 11, a more uniform light distribution can be achievedby reducing the spacing between turns of the spiral 321. The turns ofthe spiral may touch one another to form a solid fiber mat. In theseembodiments as well, light propagating along the fiber passes in adirection generally parallel to the surface of the eye, and the lightthat reaches the eye is light dispersed out of the fiber through theside walls of the fiber. The embodiments of FIGS. 10 and 11 are arrangedto treat a circular region around the central axis. In a furthervariant, the spiral dispersive fiber may extend only within an annularregion so as to treat an annular region of the cornea. In yet anothervariant, the dispersive fiber may be arranged to provide illuminationonly within regions of other shapes and sizes as, for example, a“butterfly-shaped” region as discussed above with reference to FIG. 9.

A device according to yet another embodiment of the invention (FIG. 12)includes an optically dispersive mass or shell 450, similar to theoptically dispersive shell 50 discussed above with reference to FIGS.3-6. In this embodiment, the edge surface of the dispersive shell issurrounded by an array of LEDs 402 adapted to emit UV light. Lightemitted by the LEDs passes into the optically dispersive shell 450through the edge surface 456 of the shell in much the same way as lightdispersed by the fiber in the embodiment discussed above with referenceto FIGS. 1-7. Merely by way of example, the LEDs 402 may be mountedwithin a clear polymer diode carrier 434 generally similar to the fibercarrier 34 discussed above. Desirably, the diode carrier 434 and shellare equipped with a reflective element (not shown) similar to thatdiscussed above, covering the outer surface of the shell 450, facingaway from the eye, and also covering the periphery and inner and outersurfaces of the diode carrier 434. The diode carrier and shell aremounted in a housing 462 similar to that discussed above. The LEDs arepowered by a simple electric circuit schematically indicated at 404.Circuit 404 may be connected to power and ground wires 406. In thisembodiment as well, the entire structure desirably has shape anddimension similar to that of a conventional contact lens and, thus,desirably has a maximum thickness similar to that discussed above. Thedevice may be placed in the eye of the subject with the wires extendingout of the subject's eye between the eyelids. Here again, the subjectmay close his or her eye during the procedure. Alternatively, the LED'smay be powered by wireless power transmission as discussed below.

A device according to yet another embodiment of the invention (FIG. 13)includes a housing 562 in the form of a contact lens similar to thehousings discussed above. The device of FIG. 13 further includes anantenna 501 on or within housing 562. The antenna, which may be in theform of a coil consisting of wire loops or tin oxide deposition forexample, forms a near-field resonant tank circuit. For power transfer,the antenna is linked to a rectifier and storage capacitor unit 503,which, in turn, is electrically connected to a power control circuit505. Power control circuit 505 provides regulated power voltages toother elements of the system. The structure further includes anilluminating element 530 adapted to apply light to the cornea asdiscussed above. For example, the illuminating element may include adispersive structure connected to a source of light external to thehousing by a transmission fiber as discussed herein in connection withFIGS. 1-11 and 19-25, or a dispersive element and an LED array mountedon or in the housing as discussed above in connection with FIG. 14.

A sensing element 532 is in optical communication with the illuminatingelement so that light from the illuminating element impinges on thesensing element. The sensing element is adapted to generate one or moresignals which represent the light impinging on the sensing element, andthus represent the light applied by the illuminating element.

One form of sensing element 532 is depicted in FIG. 14. This sensingelement includes one or more photosensors such as PIN diodes 534sensitive to UV light mounted in a ring 536. The ring is mounted on thehousing 562 so that the ring structure encircles the dispersive massincluded in the illuminating element 530. For example, where theilluminating structure incorporates a fiber carrier and reflectiveelement as discussed above with reference to FIGS. 1-7, the ringstructure may be disposed within the reflective element and extendaround the fiber carrier or between the fiber carrier and the dispersivemass. The ring structure may be integral with the fiber carrier. Wherethe illuminating structure includes a diode carrier and LED array asdiscussed above with reference to FIG. 12, the ring structure mayencircle the diode carrier, or may be integral with the diode carrier,and some of the LEDs included in the array may be connected to act asthe photosensors of the sensing element rather than as light emitters.The sensing element may include one or more signal processing circuits538. In the particular embodiment shown, the signal processing circuits538 include three current-to-voltage converters, each incorporating anamplifier 540 and feedback resistor 542. Only one of these converters isdepicted in FIG. 14 for clarity of illustration.

The device further includes an analog drive circuit 513 (FIG. 13)arranged to supply power to the light source 509 associated with thelight emitting element 520. For example, where the light-emittingelement includes an LED array, the drive circuit 513 supplies power tothe LEDs. Where the light-emitting element includes an external lightsource such as a laser connected to a transmission fiber, the drivecircuit supplies power to the laser. Drive circuit 513 has a set pointvalue input connected to a control circuit 515. The control circuit hasone or more inputs connected to sensing element 511. In someembodiments, all of the foregoing components can be are mounted onhousing 562. In other embodiments, the control architecture (circuits513 and 515) is located remote from the housing 562 and communicateswith the photosensor(s) of sensing element 530 either through fine wiresthe run between the lens and the control system, or wirelessly. Forwireless communication, a telemetry transmitter (not shown) may bemounted on the housing and connected to antenna 501 or to anotherantenna mounted on or in housing 562. The device further includes aradiofrequency (“RF”) transmitter 517 separate from housing 562.

In operation, RF power as, for example, at about 100 kHz, is supplied bytransmitter 517 through near field communication with antenna 501. Thepower received by antenna 501 is rectified by rectifier 503 andconditioned by power control circuit 505. The power control circuit 505supplies power to the other electronic elements which are mounted on thehousing as discussed above. The signal or signals from sensing element532 will represent a proxy proportional to the amount of light availablefor UV corneal crosslinking and serves to aid in dosimetry. Duringdelivery of the UV, control circuit compares the applied UV intensityrepresented by this photodetector generated signals to a signalrepresentative of the desired applied intensity. The control circuit 515desirably incorporates a calibration memory incorporating datarepresenting the correlation between the signal or signals from thesensing element 532 and the actual dose applied to the subject's eye.The control circuit 515 varies the set point control signal applied tothe control unit 513 so as to maintain the applied intensity at thedesired level.

In a further variant, an additional intensity sensor (not shown) islocated at a light source such as a laser external to the housing. Inthis variant, the sensing system will not only be able to control theapplied intensity, it can also serve as an error or damage detector.Unaccounted for differences between launched optical power supplied bythe light source and optical power detected by the sensing element arelikely due to damage to the fiber system or to a lens or other opticalelement.

The concept of monitoring of applied dose discussed above with referenceto FIG. 13 also may be applied to the other embodiments discussed above.For example, the embodiment discussed above with reference to FIGS. 1-6may be provided with a sensing fiber. The sensing fiber may be connectedthrough an output fiber extending parallel with transmission fiber to adiode or other photodetector mounted outside of the device housing as,for example, at the UV light source. Control circuitry responsive to thesignal from the photodetector also may be mounted outside of thehousing.

A device in accordance with a further embodiment of the invention (FIG.15) includes a contact lens-like structure 600, which may be similar toany of the structures discussed herein. In addition, the device includespairs of electrodes 601 adapted to overlie the patient's eye outside ofthe region to be treated. For example, the electrodes 601 may befastened to the housing of the device so that the electrodes are exposedat the inner surface of the housing which faces toward the eye duringuse. Merely by way of example, the electrodes may be formed frommaterials such as tin oxide, or noble metals such as gold and silver. Asdiscussed below, the electrodes are used as liquid level sensors to helpmaintain a constant liquid presence in the space between the device andthe patient's eye. The pairs of electrodes are distributed over thecircumference of the contact lens structure. In the particularembodiment illustrated, three pairs of electrodes are equally spacedaround the circumference. The electrodes of each pair desirably have aknown conductive surface area presented to the space and are spaced fromone another by a calibrated distance D_(E). For example, the electrodesmay be 0.03 inches (0.77 mm) diameter with 0.125 inches (3.2 mm)center-to-center spacing. In some cases, the inner surface of thehousing is coated with a hydrophilic layer to aid the adhesion of thedevice to the eye. This hydrophilic layer can hold a layer of conductivefluid over the surfaces of the electrodes. Such layer may besufficiently thick so that the impedance of the retained layer willapproximate the impedance of a liquid present in the space between thehousing and the eye. To prevent this, the hydrophilic layer may beomitted in areas 602 of the inner surface carrying the electrodes.

The device according to this embodiment further includes a port 603communicating with the interior surface of the housing, so that the portis open to the space between the device housing and the patient's eyeduring use. Port 603 is connected to a liquid supply conduit 605, sothat the conduit communicates with the interior surface of the contactlens structure. Supply conduit 605 may be a small-diameter capillaryconduit. The supply conduit 605 may extend alongside of the transmissionfiber supplying light to the device. The supply conduit 605 may be atubular fiber, such as a pipette or polyimide tube. In some embodiments,the conduit may additionally serve as the transmission fiber. Supplyconduit 605 is connected to a pump 607. Pump 607 is connected to asource 609 of a liquid to be applied prior to and/or during treatmentdepending on treatment protocol.

Each pair of electrodes 601 serves as an individual impedance measuringelement to acquire individual measurements. The pairs of electrodesdesirably do not interact with one another through leakage currentpaths. To accomplish this, each pair of electrodes 601 is connected toan individual sensor circuit 610.

A single one of the sensor circuits 610 is shown in FIG. 16. It includesan error amplifier A1, 628 that has one input connected to digital toanalog converter (“DAC”) 631. The output of error amplifier 628 isconnected through a current sense resistor Rs, 626 to one electrode 601of a pair. The opposite electrode of the pair is connected to ground.The impedance between the electrodes is shown schematically at 612. Anamplifier A2, 627 has inputs connected on opposite sides of currentsense resistor 626. The output of amplifier A2, 627 is connected to theother input of error amplifier A1, 628. A dedicated precision analogamplifier stage A3, 630 is connected to a circuit node between thecurrent sense resistor 626 and the electrode pair. In operation, erroramplifier 628 receives a current set point signal from DAC 631 andmaintains the current passing through the current sense resistor at aconstant level such that the output from amplifier A2, 627 is equal tothe set point signal. The voltage at node 611 and the output signal 632from amplifier stage A3, 630 thus represent the impedance 612 betweenthe electrodes of the pair.

As seen in FIG. 15, the DAC 631 may be common to all of the sensorcircuits. The output signals 632 from the individual sensor circuits arecombined with one another by an analog summing circuit 613, and thecombined signal is supplied to a control circuit 614. This combinedsignal will vary with the degree of hydration of the space between thelens-like structure and the eye. The control circuit controls pump 607so as to maintain the desired hydration. The sensor circuits and controlcircuits may be disposed outside of the contact lens structure, with thesensor circuits connected to the electrodes 601 with a simple multi-wireinterface Alternately, the signal processing may be contained “on lens”by utilizing a localized silicon IC or ASIC.

Other sensing elements may be employed, such as an interdigitated fingerarray 623 (FIG. 17) or circular interdigitated arrays 624 (FIG. 18). Theelement's measurement of impedance may be by means of either a □A(microampere) precision DC current or, alternately, a kilohertz range,AC excitation. AC excitation is typically employed in most “wetted”measurement applications.

In other embodiments, multiple sensing elements such as multipleelectrode pairs are placed on the inside surface of the device, exposedto the space between the device and the cornea. When this space isfilled with a conductive solution, all sensing elements register thesame impedance. As fluid drains or leaks out of the space, theimpedances of various elements will deviate from one another. Thisdeviation is used as a control signal to cause the pump to infuseadditional fluid until the impedances of the sensors register that eachis bathed in fluid.

In some embodiments, the sensing elements are not electrodes, butmechanically resonant elements. A shift in the measured resonantfrequency or mechanical impedance can be used as a pump control signalin place of a shift in the electrical impedance discussed previously.

The feedback control system shown in FIG. 12 can be varied and, indeed,in some embodiments, can be omitted. Thus, liquid can be supplied underpressure through conduit 605 without any feedback control.

Embodiments of the invention that incorporate a fluid sensing system canbe employed in one method of the corneal collagen crosslinking procedurewhereby the device is placed on the eye during the preparation phase ofthe procedure, and a photoactive agent containing solution is pumpedinto the space between the lens and the cornea to enable cornealsaturation with the photoactive agent such as riboflavin. The sensingsystems ensure the reservoir is full throughout this saturation phase.After sufficient time, the pump is activated to deliver a wettingsolution without riboflavin to flush the reservoir space, as anyriboflavin in this space will prevent some of the UV from reaching thecornea. Once flushed, the pump and sensing system then maintains a wetcorneal surface throughout the UV delivery phase.

A device according to a further embodiment of the invention (FIGS.19-21) includes an optical structure 700 that incorporates a reflector702. Reflector 702 includes an inner element 704 that defines a firstinterior surface 706 in the form of a surface generally corresponding tothe shape of the cornea and having a central axis 722. The interiorelement additionally defines an aperture 710, which, in this instance,is a circular aperture concentric with axis 722. The interior elementhas a reflective circumferential surface 712 in the form of a cylinderconcentric with axis 722. The interior element 704 also has a ledgesurface 714 extending from the aperture 710 to the circumferentialsurface 712. Ledge surface 714 faces in the outward direction (towardsthe top of the drawing in FIG. 21), as indicated by the arrow O. Ledgesurface 714 desirably also is a reflective surface.

Reflector 702 further includes an outer element 716 overlying theoutward extremity of the inner element 704. Outer element 716 is shownin transparent, phantom view in FIG. 19 for clarity of illustration. Theouter element is secured to the inner element as, for example, byinterlocking ridges 718 at the periphery of these elements, remote fromaxis 722. The outer element 716 defines a reflective surface, referredto herein as the “cap surface” 720, extending across axis 722 and spacedapart from ledge surface 714. Reflector 702 thus defines a cavity 724(FIG. 21) communicating with aperture 710. The cavity is bounded in partby the circumferential reflective surface 712 and the reflective capsurface 720 and.

The reflective surfaces 712, 720, and 714 of the reflector may bearranged to provide either specular reflection or diffuse reflection.For example, the elements of the reflector may be formed from a metalsuch as aluminum with polished surfaces to provide specular reflectionor with roughened surfaces to provide diffuse reflection. Alternatively,the elements of the reflector may be formed form a material such as apolymer coated with a metal such as aluminum. In yet anotherarrangement, the reflective surfaces may be formed by materials thatprovide a highly efficient diffuse reflection in the wavelengths to beapplied. For example, films suitable for providing diffuse reflection ofultraviolet and blue light are commercially available from the 3MCompany of Minneapolis, Minn. USA.

An optically dispersive element 726, such as a mass of a dispersivecomposition as discussed above, is disposed within cavity 724. Thedispersive element is generally in the form of a disc concentric withaxis 722. It has an outer surface 728 facing outwardly and confrontingthe cap surface 720 of the reflector and an inner surface 730 facinginwardly. The inner surface includes a portion overlying ledge surface714 of the reflector, as well as a portion extending across aperture710. This portion of the inner surface projects into the aperture sothat it defines a surface region continuous with the first inner surface706 of the reflector. The dispersive element 726 also defines an edgesurface 732, which is in the form of a cylinder concentric with axis722. The diameter of edge surface 732 is slightly smaller than thediameter of circumferential surface 712 of the reflector, so that thedispersive element and reflector cooperatively define an annular gap 734extending around the dispersive element. Gap 734 is filled with a clearmaterial, which may be a solid or gel, a liquid, or a gas such as air.The edge surface 732 of the dispersive element is in opticalcommunication with the circumferential surface 712 of the reflector.

The reflector further defines a bore 740 (FIGS. 19, 20) extendingthrough the inner and outer elements in a plane transverse to thecentral axis 722. In the particular embodiment depicted, the bore 740extends in a plane perpendicular to the axis. Bore 740 communicates withthe interior of cavity 724 and, in particular, with gap 734. As bestseen in FIG. 20, bore 740 communicates with the cavity and gap at alocation near to the reflective circumferential surface 712. Atransmission optical fiber 742 extends through the port 740 and is heldin place by a coupler 744 in the form of a sleeve that surrounds thefiber. The coupler 744 is secured to the fiber and to the internal wallof bore 740 as, for example, by an adhesive.

Fiber 742 has a distal end 746 and a proximal end (not shown). Theproximal end is equipped with an appropriate coupler (not shown) forengagement with a light source such as light source 30 (FIG. 1). Thedistal end 746 extends coaxially with bore 740 and thus extends in aplane transverse to and preferably perpendicular to axis 722. The distalend 746 of the fiber is positioned within gap 734 adjacent thecircumferential reflective surface 712. As seen in FIG. 20, viewing thedistal end of the fiber in a plane transverse to the axis, the distalend of the fiber may extend in a direction that is tangential to thecircumferential surface 712 or that lies at an angle A_(DE) to such atangent.

The optical structure 700, including the reflector and dispersiveelement, is mounted in a housing 762. As best seen in FIG. 19, thehousing 762 may encompass a portion of the fiber 742 and coupler 744extending out of the reflector. As in the embodiments discussed above,housing 762 is a generally shell-shaped structure, desirably less than 3mm thick, having an interior surface generally conforming to the shapeof a surface of the eye. For example, the housing 762 may have a firstinterior surface portion 764 that constitutes a continuation of thefirst interior surface 706 defined by the reflector and by the innersurface of dispersive element 726, so as to form a composite firstinterior surface generally conforming to the shape of the cornea of theeye. In the particular embodiment depicted, housing 762 further includesa second interior surface portion 766 corresponding to the shape of thesclera of the eye. Here again, the assembly including the opticalstructure 700 and housing 762 forms a thin shell having an interiorsurface corresponding to the shape of the eye, so that the entirestructure is generally of the form and size of a conventional scleralcontact lens. As discussed above, the second surface portion 766 may beomitted so that the entire structure will have the form and size of aconventional conical contact lens. Here again, the interior surfaces ofthe housing and of the optical structure may be covered with a film of ahydrophilic material (not shown).

In operation, the assembly is positioned on the eye with the innersurfaces overlying the corresponding surfaces of the eye in much thesame manner as discussed above with reference to FIG. 7. In thiscondition, the inward direction of the optical assembly constitutes thedirection toward the eye of the patient, whereas the outward directionis the direction away from the eye of the patient. Aperture 710 isaligned with the region of the cornea to be treated.

While the assembly is in this position, light is directed into cavity724 through the transmission fiber 742. Light passes from the distal end746 of the fiber, strikes the reflective circumferential surface, and isreflected along a path around the periphery of the dispersive element.This path is schematically indicated in part by the path L in FIG. 20.

The light path L depicted in FIG. 20 is simplified for purposes ofillustration. For example, the light may be refracted as it passesbetween the gap 734 and the dispersive element 726. Depending upon theindices of refraction of the medium in gap 734 and the dispersiveelement, the interface between the dispersive element and the gap mayserve to confine the light to within the gap, so that the dispersiveelement and the circumferential reflective surface 712 serve as anannular light guide to help direct the light around the circumference ofthe structure.

As the light propagates around the structure, some of the light will bedirected inwardly, toward axis 722. Some of the light will be spread inthe inward and outward directions (FIG. 21) and thus may encounter thereflective cap surface 720 (id.) and the reflective ledge surface 714.In general, the light propagates inwardly towards the central axis 722and thus travels in directions generally parallel to the inner and outersurfaces of the dispersive element. As in the embodiments discussedabove, the light passing through the dispersive element is dispersed indirections transverse to the inner and outer surfaces of the element, sothat some of this light is dispersed in the inward direction and exitsthrough aperture 710 into the eye. In the manner discussed above, thelight performs the desired therapy as, for example, crosslinking of thecollagen in the cornea. As in the embodiments discussed above, the eyedesirably is treated with a crosslinking agent.

The embodiment discussed above with reference to FIGS. 19 and 20provides several significant advantages. It avoids the cost andcomplexity associated with the dispersive optical fiber. There is noneed for a splice between the transmission fiber 742 and a dispersivefiber. Moreover, because the transmission fiber is optically coupleddirectly to the interior of the cavity and directly to the dispersiveelement 726, without passing through any other dispersive element lighttransmitted along the transmission fiber will be efficiently coupledinto dispersive element 726. The structure according to this embodimentalso provides advantages in patient comfort and ease of therapeuticapplications similar to those discussed above. Here again, the patientneed not hold his or her eye open during the procedure and desirably mayclose or blink his or her eye freely.

An optical structure 800 used in a further embodiment of the inventionis schematically depicted in FIG. 22. This structure is identical to theoptical structure 700 discussed above with reference to FIGS. 19-21.However, in structure 800, the dispersive element 826 has a diameterequal to the diameter of the reflective circumferential surface 812, sothat the edge surface 832 of the dispersive element is in contact withthe circumferential reflective surface. Also, in this embodiment, thedistal end 846 of the transmission optical fiber is disposed within thedispersive element, near the edge surface 832 and circumferentialsurface 812. Placing the distal end of the optical fiber within thedispersive element facilitates efficient optical coupling of the lightemanating from the transmission fiber into the dispersive element. Inthe particular embodiment shown, dispersive element 826 has a gradedcomposition. It has low dispersion (long extinction length) in aperipheral region 827 disposed remote from axis 822, near the edgesurface and near the circumferential surface 812 of the reflector, andhas higher dispersion (shorter extinction length) in a central region829 near axis 822 and thus near the aperture 810 of the reflector. Asdepicted, the gradation is stepwise. However, the gradation can becontinuous.

The embodiments discussed above with reference to FIGS. 19-22 can bevaried in numerous other ways. For example, the circumferential surfaceof the reflector, and the edge surface of the dispersive element neednot be cylindrical surfaces. For example, they may be surfaces ofrevolution other than cylinders. In one embodiment, the circumferentialsurface of the reflector may be a conical shape so as to direct lightreflected from this surface along a path having a component of directionin the inward or outward direction. For example, in the embodiment ofFIGS. 19-21, the reflective surface may be arranged to direct the lightwith a component in the outward direction so that the light encountersthe reflective cap surface 720, in the inward direction such that thelight encounters the reflective ledge surface 714, or both. More complexsurfaces of revolution such as a surface defined by a curve of arbitraryshape revolved around the central axis 722 may be employed. Indeed, theedge surface of the dispersive element and the circumferential surfaceof the reflector need not be surfaces of revolution. For example, thesesurfaces may be polygonal or of irregular shape. Individual portions ofsuch surfaces may be tilted at arbitrary angles so as to reflect thelight along trajectories having inward or outward components. Also, thecap surface 720 need not be planar and need not be contiguous with theouter surface of the dispersive element.

The transmission fiber need not be secured to the optical structurewhich includes the dispersive element. As schematically represented inFIG. 23, an optical structure 900 as discussed herein may include afeature such as a socket 902, and a transmission fiber 904 may have adistal end 906 arranged to mechanically engage with the socket 902 so asto place the distal end of the fiber in optical communication with theelements in the optical structure 900 that serves to disperse light. Forexample, in the embodiments of FIGS. 19-22, the socket would be arrangedto hold the distal end of the fiber within the cavity of the reflector.In other embodiments, where a dispersive fiber is used, the socket andthe distal end of the fiber would be arranged so that when the distalend of the fiber is engaged in the socket, the distal end of the fiberwill be aligned with the dispersive fiber and in optical communicationtherewith. In the particular structure shown in FIG. 25, the distal endof the fiber is equipped with a collar 908 having a tapered exterioradapted to fit within a tapered interior defined by the socket 902.However, other mechanical configurations can be employed. For example,the distal end of the fiber may be bare, and the feature may define anopening adapted to engage the outside of the fiber directly, without anyintervening collar or other structure. Other expedients for promotingoptical coupling between the transmission fiber and other elements ofthe system can be used. For example, where the transmission fiber is tobe coupled to a dispersive fiber, elements such as index-matching gelsmay be used to provide an optically efficient splice.

Use of a transmission fiber that is detachable from the opticalstructure and from the contact lens structure as a whole allows reuse ofthe transmission fiber with a different contact lens structure. Forexample, the contact lens structure may be used once and discarded so asto avoid the risk of infection, whereas the transmission fiber may bereused.

The optical structure need not be permanently mounted to a housing thathelps in positioning the optical structure on the eye of the patient. Asschematically depicted in FIG. 24, an optical structure 1000 is used inconjunction with a separate, detachable housing 1062. The opticalstructure 1000 may include any of the optical arrangements discussedabove. Desirably, the optical structure 1000 includes the elements inthe optical path between the transmission optical fiber 1002 and theaperture 1004, including one or more optically dispersive elements and,desirably, one or more reflective elements as discussed herein. Housing1062 has one or more inner surfaces 1006 with a shape generallycorresponding to the shape of a surface of an eye. For example, theinner surface 1006 may include a first surface having a shape generallycorresponding to the shape of the cornea and may also include a secondsurface generally corresponding to the shape of the sclera as discussedabove, or may include only the first surface. The inner surface 1006defines an axis 1022, which extends towards and away from the eye whenthe inner surface 1006 overlies the surface of the eye. For example,axis 1022 may be aligned with the optical axis of the eye as discussedabove. Housing 1062 also includes a wall 1008, which extends across theaxis. Desirably, wall 1008 is arranged to transmit light at a wavelengthto be applied to the eye. In the embodiments discussed herein, which arearranged to provide crosslinking, wall 1008 may be arranged to transmitlight in the UV or blue wavelength bands.

The housing further includes a feature 1010 adapted to releasably engageoptical structure 1000. In the embodiment depicted in FIG. 24, feature1010 is shown as a simple tapered socket arranged to mate with acorresponding tapered wall on the outside of the optical structure 1000.However, feature 1010 may include any other element capable of engagingthe optical structure as, for example, other forms of mechanicalfeatures capable of mating with corresponding mechanical features on theoptical structure. Feature 1010 is arranged to hold the opticalstructure so that the aperture 1004 of the optical structure is alignedwith axis 1022 and wall 1008 and so that the optical structure isseparated from the eye E by wall 1008.

Desirably, housing 1062 is provided as a single-use device, whereas theoptical structure 1000 is reusable. In a method according to a furtherembodiment of the invention, plural patients can be treated using thesame optical structure. First, the optical structure with is assembledwith a housing 1062. The assembly is placed over the eye of a firstpatient, so that the wall of the housing is disposed between the opticalstructure and the eye and so that the housing engages the eye andmaintains the optical structure out of contact with the eye. The opticalstructure is then actuated as discussed above so that light is dispersedwithin the optical housing and passes out of the aperture 1004 andthrough the wall 1008 of the housing into the eye of the patient toperform the desired therapy. Following this step, the optical structureis disassembled from the housing and the foregoing steps are repeatedusing a different housing and, typically, a different patient on eachrepetition. The different housings may have different shapes or sizes toaccommodate the needs of different patients.

A structure according to a further embodiment of the invention (FIG. 25)incorporates a dispersive element 1100 having an inner surface 1102 thatfaces inwardly toward the eye when the device is in place on the eye andan outer surface 1104 that faces outwardly away from the eye. Thedispersive element has an axis 1122 extending through these surfaces. Atransmission optical fiber has a distal end 1106 disposed on axis 1122and spaced outwardly from the outer surface 1104. An opticallytransmissive medium 1107 is provided between the distal end of the fiberand the outer surface, so that the distal end of the transmission fiberis in optical communication with the outer surface 1104. The distal endof the fiber is equipped with one or more spreading structuresschematically indicated at 1108. The spreading structures may includeelements such as a mass of dispersive material, one or more reflectors,refractive elements, and configuration of the cleaved fiber end.Alternatively or additionally, the medium 1107 may have dispersive orrefracting properties that serve to spread the light. The spreadingstructures are arranged to direct light supplied through the fiber awayfrom axis 1122 so that the light impinges on an outer surface over asubstantial region of the outer surface and desirably over the entireouter surface. The structure may further include a reflective elementdefining one or more of a circumferential reflective surface 1112extending around the axis, an inwardly facing reflective cap surface1114 disposed outward of the fiber distal end, and an outwardly facingreflective ledge surface 1116 facing the inner surface of the dispersiveelement.

As these and other variations and combinations of the features discussedabove can be utilized without departing from the present invention asdefined by the claims, the foregoing description of the preferredembodiments should be taken by way of illustration rather than by way oflimitation of the present invention.

1. A method of applying light to the eye of a subject comprisingdirecting light in a direction generally parallel to the surface of thecornea of the eye within an optically dispersive element overlying thesurface of the cornea so that light dispersed by the element passes outof the element and into the cornea.